networking/telnet.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * telnet implementation for busybox
   4  *
   5  * Author: Tomi Ollila <too@iki.fi>
   6  * Copyright (C) 1994-2000 by Tomi Ollila
   7  *
   8  * Created: Thu Apr  7 13:29:41 1994 too
   9  * Last modified: Fri Jun  9 14:34:24 2000 too
  10  *
  11  * Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
  12  *
  13  * HISTORY
  14  * Revision 3.1  1994/04/17  11:31:54  too
  15  * initial revision
  16  * Modified 2000/06/13 for inclusion into BusyBox by Erik Andersen <andersen@codepoet.org>
  17  * Modified 2001/05/07 to add ability to pass TTYPE to remote host by Jim McQuillan
  18  * <jam@ltsp.org>
  19  * Modified 2004/02/11 to add ability to pass the USER variable to remote host
  20  * by Fernando Silveira <swrh@gmx.net>
  21  *
  22  */
  23
  24 #include <termios.h>
  25 #include <arpa/telnet.h>
  26 #include <netinet/in.h>
  27 #include "busybox.h"
  28
  29 #ifdef DOTRACE
  30 #include <arpa/inet.h> /* for inet_ntoa()... */
  31 #define TRACE(x, y) do { if (x) printf y; } while (0)
  32 #else
  33 #define TRACE(x, y)
  34 #endif
  35
  36 #define DATABUFSIZE  128
  37 #define IACBUFSIZE   128
  38
  39 enum {
  40         CHM_TRY = 0,
  41         CHM_ON = 1,
  42         CHM_OFF = 2,
  43
  44         UF_ECHO = 0x01,
  45         UF_SGA = 0x02,
  46
  47         TS_0 = 1,
  48         TS_IAC = 2,
  49         TS_OPT = 3,
  50         TS_SUB1 = 4,
  51         TS_SUB2 = 5,
  52 };
  53
  54 #define WriteCS(fd, str) write(fd, str, sizeof str -1)
  55
  56 typedef unsigned char byte;
  57
  58 /* use globals to reduce size ??? */ /* test this hypothesis later */
  59 static struct Globalvars {
  60         int             netfd; /* console fd:s are 0 and 1 (and 2) */
  61     /* same buffer used both for network and console read/write */
  62         char    buf[DATABUFSIZE]; /* allocating so static size is smaller */
  63         byte    telstate; /* telnet negotiation state from network input */
  64         byte    telwish;  /* DO, DONT, WILL, WONT */
  65         byte    charmode;
  66         byte    telflags;
  67         byte    gotsig;
  68         byte    do_termios;
  69         /* buffer to handle telnet negotiations */
  70         char    iacbuf[IACBUFSIZE];
  71         short   iaclen; /* could even use byte */
  72         struct termios termios_def;
  73         struct termios termios_raw;
  74 } G;
  75
  76 #define xUSE_GLOBALVAR_PTR /* xUSE... -> don't use :D (makes smaller code) */
  77
  78 #ifdef USE_GLOBALVAR_PTR
  79 struct Globalvars * Gptr;
  80 #define G (*Gptr)
  81 #endif
  82
  83 static void iacflush(void)
  84 {
  85         write(G.netfd, G.iacbuf, G.iaclen);
  86         G.iaclen = 0;
  87 }
  88
  89 /* Function prototypes */
  90 static void rawmode(void);
  91 static void cookmode(void);
  92 static void do_linemode(void);
  93 static void will_charmode(void);
  94 static void telopt(byte c);
  95 static int subneg(byte c);
  96
  97 /* Some globals */
  98 static const int one = 1;
  99
 100 #ifdef CONFIG_FEATURE_TELNET_TTYPE
 101 static char *ttype;
 102 #endif
 103
 104 #ifdef CONFIG_FEATURE_TELNET_AUTOLOGIN
 105 static const char *autologin;
 106 #endif
 107
 108 #ifdef CONFIG_FEATURE_AUTOWIDTH
 109 static int win_width, win_height;
 110 #endif
 111
 112 static void doexit(int ev)
 113 {
 114         cookmode();
 115         exit(ev);
 116 }
 117
 118 static void conescape(void)
 119 {
 120         char b;
 121
 122         if (G.gotsig)   /* came from line  mode... go raw */
 123                 rawmode();
 124
 125         WriteCS(1, "\r\nConsole escape. Commands are:\r\n\n"
 126                         " l     go to line mode\r\n"
 127                         " c     go to character mode\r\n"
 128                         " z     suspend telnet\r\n"
 129                         " e     exit telnet\r\n");
 130
 131         if (read(0, &b, 1) <= 0)
 132                 doexit(1);
 133
 134         switch (b)
 135         {
 136         case 'l':
 137                 if (!G.gotsig)
 138                 {
 139                         do_linemode();
 140                         goto rrturn;
 141                 }
 142                 break;
 143         case 'c':
 144                 if (G.gotsig)
 145                 {
 146                         will_charmode();
 147                         goto rrturn;
 148                 }
 149                 break;
 150         case 'z':
 151                 cookmode();
 152                 kill(0, SIGTSTP);
 153                 rawmode();
 154                 break;
 155         case 'e':
 156                 doexit(0);
 157         }
 158
 159         WriteCS(1, "continuing...\r\n");
 160
 161         if (G.gotsig)
 162                 cookmode();
 163
 164  rrturn:
 165         G.gotsig = 0;
 166
 167 }
 168 static void handlenetoutput(int len)
 169 {
 170         /*      here we could do smart tricks how to handle 0xFF:s in output
 171          *      stream  like writing twice every sequence of FF:s (thus doing
 172          *      many write()s. But I think interactive telnet application does
 173          *      not need to be 100% 8-bit clean, so changing every 0xff:s to
 174          *      0x7f:s
 175          *
 176          *      2002-mar-21, Przemyslaw Czerpak (druzus@polbox.com)
 177          *      I don't agree.
 178          *      first - I cannot use programs like sz/rz
 179          *      second - the 0x0D is sent as one character and if the next
 180          *               char is 0x0A then it's eaten by a server side.
 181          *      third - whay doy you have to make 'many write()s'?
 182          *              I don't understand.
 183          *      So I implemented it. It's realy useful for me. I hope that
 184          *      others people will find it interesting to.
 185          */
 186
 187         int i, j;
 188         byte * p = (byte*)G.buf;
 189         byte outbuf[4*DATABUFSIZE];
 190
 191         for (i = len, j = 0; i > 0; i--, p++)
 192         {
 193                 if (*p == 0x1d)
 194                 {
 195                         conescape();
 196                         return;
 197                 }
 198                 outbuf[j++] = *p;
 199                 if (*p == 0xff)
 200                         outbuf[j++] = 0xff;
 201                 else if (*p == 0x0d)
 202                         outbuf[j++] = 0x00;
 203         }
 204         if (j > 0 )
 205                 write(G.netfd, outbuf, j);
 206 }
 207
 208
 209 static void handlenetinput(int len)
 210 {
 211         int i;
 212         int cstart = 0;
 213
 214         for (i = 0; i < len; i++)
 215         {
 216                 byte c = G.buf[i];
 217
 218                 if (G.telstate == 0) /* most of the time state == 0 */
 219                 {
 220                         if (c == IAC)
 221                         {
 222                                 cstart = i;
 223                                 G.telstate = TS_IAC;
 224                         }
 225                 }
 226                 else
 227                         switch (G.telstate)
 228                          {
 229                          case TS_0:
 230                                  if (c == IAC)
 231                                          G.telstate = TS_IAC;
 232                                  else
 233                                          G.buf[cstart++] = c;
 234                                  break;
 235
 236                          case TS_IAC:
 237                                  if (c == IAC) /* IAC IAC -> 0xFF */
 238                                  {
 239                                          G.buf[cstart++] = c;
 240                                          G.telstate = TS_0;
 241                                          break;
 242                                  }
 243                                  /* else */
 244                                  switch (c)
 245                                  {
 246                                  case SB:
 247                                          G.telstate = TS_SUB1;
 248                                          break;
 249                                  case DO:
 250                                  case DONT:
 251                                  case WILL:
 252                                  case WONT:
 253                                          G.telwish =  c;
 254                                          G.telstate = TS_OPT;
 255                                          break;
 256                                  default:
 257                                          G.telstate = TS_0;     /* DATA MARK must be added later */
 258                                  }
 259                                  break;
 260                          case TS_OPT: /* WILL, WONT, DO, DONT */
 261                                  telopt(c);
 262                                  G.telstate = TS_0;
 263                                  break;
 264                          case TS_SUB1: /* Subnegotiation */
 265                          case TS_SUB2: /* Subnegotiation */
 266                                  if (subneg(c))
 267                                          G.telstate = TS_0;
 268                                  break;
 269                          }
 270         }
 271         if (G.telstate)
 272         {
 273                 if (G.iaclen)                   iacflush();
 274                 if (G.telstate == TS_0) G.telstate = 0;
 275
 276                 len = cstart;
 277         }
 278
 279         if (len)
 280                 write(1, G.buf, len);
 281 }
 282
 283
 284 /* ******************************* */
 285
 286 static void putiac(int c)
 287 {
 288         G.iacbuf[G.iaclen++] = c;
 289 }
 290
 291
 292 static void putiac2(byte wwdd, byte c)
 293 {
 294         if (G.iaclen + 3 > IACBUFSIZE)
 295                 iacflush();
 296
 297         putiac(IAC);
 298         putiac(wwdd);
 299         putiac(c);
 300 }
 301
 302 #ifdef CONFIG_FEATURE_TELNET_TTYPE
 303 static void putiac_subopt(byte c, char *str)
 304 {
 305         int     len = strlen(str) + 6;   // ( 2 + 1 + 1 + strlen + 2 )
 306
 307         if (G.iaclen + len > IACBUFSIZE)
 308                 iacflush();
 309
 310         putiac(IAC);
 311         putiac(SB);
 312         putiac(c);
 313         putiac(0);
 314
 315         while (*str)
 316                 putiac(*str++);
 317
 318         putiac(IAC);
 319         putiac(SE);
 320 }
 321 #endif
 322
 323 #ifdef CONFIG_FEATURE_TELNET_AUTOLOGIN
 324 static void putiac_subopt_autologin(void)
 325 {
 326         int len = strlen(autologin) + 6;        // (2 + 1 + 1 + strlen + 2)
 327         char *user = "USER";
 328
 329         if (G.iaclen + len > IACBUFSIZE)
 330                 iacflush();
 331
 332         putiac(IAC);
 333         putiac(SB);
 334         putiac(TELOPT_NEW_ENVIRON);
 335         putiac(TELQUAL_IS);
 336         putiac(NEW_ENV_VAR);
 337
 338         while (*user)
 339                 putiac(*user++);
 340
 341         putiac(NEW_ENV_VALUE);
 342
 343         while (*autologin)
 344                 putiac(*autologin++);
 345
 346         putiac(IAC);
 347         putiac(SE);
 348 }
 349 #endif
 350
 351 #ifdef CONFIG_FEATURE_AUTOWIDTH
 352 static void putiac_naws(byte c, int x, int y)
 353 {
 354         if (G.iaclen + 9 > IACBUFSIZE)
 355                 iacflush();
 356
 357         putiac(IAC);
 358         putiac(SB);
 359         putiac(c);
 360
 361         putiac((x >> 8) & 0xff);
 362         putiac(x & 0xff);
 363         putiac((y >> 8) & 0xff);
 364         putiac(y & 0xff);
 365
 366         putiac(IAC);
 367         putiac(SE);
 368 }
 369 #endif
 370
 371 /* void putiacstring (subneg strings) */
 372
 373 /* ******************************* */
 374
 375 static char const escapecharis[] = "\r\nEscape character is ";
 376
 377 static void setConMode(void)
 378 {
 379         if (G.telflags & UF_ECHO)
 380         {
 381                 if (G.charmode == CHM_TRY) {
 382                         G.charmode = CHM_ON;
 383                         printf("\r\nEntering character mode%s'^]'.\r\n", escapecharis);
 384                         rawmode();
 385                 }
 386         }
 387         else
 388         {
 389                 if (G.charmode != CHM_OFF) {
 390                         G.charmode = CHM_OFF;
 391                         printf("\r\nEntering line mode%s'^C'.\r\n", escapecharis);
 392                         cookmode();
 393                 }
 394         }
 395 }
 396
 397 /* ******************************* */
 398
 399 static void will_charmode(void)
 400 {
 401         G.charmode = CHM_TRY;
 402         G.telflags |= (UF_ECHO | UF_SGA);
 403         setConMode();
 404
 405         putiac2(DO, TELOPT_ECHO);
 406         putiac2(DO, TELOPT_SGA);
 407         iacflush();
 408 }
 409
 410 static void do_linemode(void)
 411 {
 412         G.charmode = CHM_TRY;
 413         G.telflags &= ~(UF_ECHO | UF_SGA);
 414         setConMode();
 415
 416         putiac2(DONT, TELOPT_ECHO);
 417         putiac2(DONT, TELOPT_SGA);
 418         iacflush();
 419 }
 420
 421 /* ******************************* */
 422
 423 static void to_notsup(char c)
 424 {
 425         if      (G.telwish == WILL)     putiac2(DONT, c);
 426         else if (G.telwish == DO)       putiac2(WONT, c);
 427 }
 428
 429 static void to_echo(void)
 430 {
 431         /* if server requests ECHO, don't agree */
 432         if      (G.telwish == DO) {     putiac2(WONT, TELOPT_ECHO);     return; }
 433         else if (G.telwish == DONT)     return;
 434
 435         if (G.telflags & UF_ECHO)
 436         {
 437                 if (G.telwish == WILL)
 438                         return;
 439         }
 440         else
 441                 if (G.telwish == WONT)
 442                         return;
 443
 444         if (G.charmode != CHM_OFF)
 445                 G.telflags ^= UF_ECHO;
 446
 447         if (G.telflags & UF_ECHO)
 448                 putiac2(DO, TELOPT_ECHO);
 449         else
 450                 putiac2(DONT, TELOPT_ECHO);
 451
 452         setConMode();
 453         WriteCS(1, "\r\n");  /* sudden modec */
 454 }
 455
 456 static void to_sga(void)
 457 {
 458         /* daemon always sends will/wont, client do/dont */
 459
 460         if (G.telflags & UF_SGA)
 461         {
 462                 if (G.telwish == WILL)
 463                         return;
 464         }
 465         else
 466                 if (G.telwish == WONT)
 467                         return;
 468
 469         if ((G.telflags ^= UF_SGA) & UF_SGA) /* toggle */
 470                 putiac2(DO, TELOPT_SGA);
 471         else
 472                 putiac2(DONT, TELOPT_SGA);
 473
 474         return;
 475 }
 476
 477 #ifdef CONFIG_FEATURE_TELNET_TTYPE
 478 static void to_ttype(void)
 479 {
 480         /* Tell server we will (or won't) do TTYPE */
 481
 482         if(ttype)
 483                 putiac2(WILL, TELOPT_TTYPE);
 484         else
 485                 putiac2(WONT, TELOPT_TTYPE);
 486
 487         return;
 488 }
 489 #endif
 490
 491 #ifdef CONFIG_FEATURE_TELNET_AUTOLOGIN
 492 static void to_new_environ(void)
 493 {
 494         /* Tell server we will (or will not) do AUTOLOGIN */
 495
 496         if (autologin)
 497                 putiac2(WILL, TELOPT_NEW_ENVIRON);
 498         else
 499                 putiac2(WONT, TELOPT_NEW_ENVIRON);
 500
 501         return;
 502 }
 503 #endif
 504
 505 #ifdef CONFIG_FEATURE_AUTOWIDTH
 506 static void to_naws(void)
 507 {
 508         /* Tell server we will do NAWS */
 509         putiac2(WILL, TELOPT_NAWS);
 510         return;
 511 }
 512 #endif
 513
 514 static void telopt(byte c)
 515 {
 516         switch (c)
 517         {
 518                 case TELOPT_ECHO:               to_echo();      break;
 519                 case TELOPT_SGA:                to_sga();       break;
 520 #ifdef CONFIG_FEATURE_TELNET_TTYPE
 521                 case TELOPT_TTYPE:              to_ttype();break;
 522 #endif
 523 #ifdef CONFIG_FEATURE_TELNET_AUTOLOGIN
 524                 case TELOPT_NEW_ENVIRON:        to_new_environ();       break;
 525 #endif
 526 #ifdef CONFIG_FEATURE_AUTOWIDTH
 527                 case TELOPT_NAWS:               to_naws();
 528                                                                 putiac_naws(c, win_width, win_height);
 529                                                                 break;
 530 #endif
 531                 default:                                to_notsup(c);
 532                                                                 break;
 533         }
 534 }
 535
 536
 537 /* ******************************* */
 538
 539 /* subnegotiation -- ignore all (except TTYPE,NAWS) */
 540
 541 static int subneg(byte c)
 542 {
 543         switch (G.telstate)
 544         {
 545         case TS_SUB1:
 546                 if (c == IAC)
 547                         G.telstate = TS_SUB2;
 548 #ifdef CONFIG_FEATURE_TELNET_TTYPE
 549                 else
 550                 if (c == TELOPT_TTYPE)
 551                         putiac_subopt(TELOPT_TTYPE,ttype);
 552 #endif
 553 #ifdef CONFIG_FEATURE_TELNET_AUTOLOGIN
 554                 else
 555                 if (c == TELOPT_NEW_ENVIRON)
 556                         putiac_subopt_autologin();
 557 #endif
 558                 break;
 559         case TS_SUB2:
 560                 if (c == SE)
 561                         return TRUE;
 562                 G.telstate = TS_SUB1;
 563                 /* break; */
 564         }
 565         return FALSE;
 566 }
 567
 568 /* ******************************* */
 569
 570 static void fgotsig(int sig)
 571 {
 572         G.gotsig = sig;
 573 }
 574
 575
 576 static void rawmode(void)
 577 {
 578         if (G.do_termios) tcsetattr(0, TCSADRAIN, &G.termios_raw);
 579 }
 580
 581 static void cookmode(void)
 582 {
 583         if (G.do_termios) tcsetattr(0, TCSADRAIN, &G.termios_def);
 584 }
 585
 586 int telnet_main(int argc, char** argv)
 587 {
 588         char *host;
 589         int port;
 590         int len;
 591 #ifdef USE_POLL
 592         struct pollfd ufds[2];
 593 #else
 594         fd_set readfds;
 595         int maxfd;
 596 #endif
 597
 598 #ifdef CONFIG_FEATURE_AUTOWIDTH
 599         get_terminal_width_height(0, &win_width, &win_height);
 600 #endif
 601
 602 #ifdef CONFIG_FEATURE_TELNET_TTYPE
 603         ttype = getenv("TERM");
 604 #endif
 605
 606         /* memset(&G, 0, sizeof G); - already is */
 607
 608         if (tcgetattr(0, &G.termios_def) >= 0) {
 609                 G.do_termios = 1;
 610                 G.termios_raw = G.termios_def;
 611                 cfmakeraw(&G.termios_raw);
 612         }
 613
 614         if (argc < 2)
 615                 bb_show_usage();
 616
 617 #ifdef CONFIG_FEATURE_TELNET_AUTOLOGIN
 618         if (1 & getopt32(argc, argv, "al:", &autologin))
 619                 autologin = getenv("USER");
 620
 621         if (optind < argc) {
 622                 host = argv[optind++];
 623                 port = bb_lookup_port((optind < argc) ? argv[optind++] :
 624                                 "telnet", "tcp", 23);
 625                 if (optind < argc)
 626                         bb_show_usage();
 627         } else
 628                 bb_show_usage();
 629 #else
 630         host = argv[1];
 631         port = bb_lookup_port((argc > 2) ? argv[2] : "telnet", "tcp", 23);
 632 #endif
 633         G.netfd = create_and_connect_stream_or_die(host, port);
 634
 635         setsockopt(G.netfd, SOL_SOCKET, SO_KEEPALIVE, &one, sizeof one);
 636
 637         signal(SIGINT, fgotsig);
 638
 639 #ifdef USE_POLL
 640         ufds[0].fd = 0; ufds[1].fd = G.netfd;
 641         ufds[0].events = ufds[1].events = POLLIN;
 642 #else
 643         FD_ZERO(&readfds);
 644         FD_SET(0, &readfds);
 645         FD_SET(G.netfd, &readfds);
 646         maxfd = G.netfd + 1;
 647 #endif
 648
 649         while (1) {
 650 #ifndef USE_POLL
 651                 fd_set rfds = readfds;
 652
 653                 switch (select(maxfd, &rfds, NULL, NULL, NULL))
 654 #else
 655                 switch (poll(ufds, 2, -1))
 656 #endif
 657                 {
 658                 case 0:
 659                         /* timeout */
 660                 case -1:
 661                         /* error, ignore and/or log something, bay go to loop */
 662                         if (G.gotsig)
 663                                 conescape();
 664                         else
 665                                 sleep(1);
 666                         break;
 667                 default:
 668
 669 #ifdef USE_POLL
 670                         if (ufds[0].revents) /* well, should check POLLIN, but ... */
 671 #else
 672                         if (FD_ISSET(0, &rfds))
 673 #endif
 674                         {
 675                                 len = read(0, G.buf, DATABUFSIZE);
 676
 677                                 if (len <= 0)
 678                                         doexit(0);
 679
 680                                 TRACE(0, ("Read con: %d\n", len));
 681
 682                                 handlenetoutput(len);
 683                         }
 684
 685 #ifdef USE_POLL
 686                         if (ufds[1].revents) /* well, should check POLLIN, but ... */
 687 #else
 688                         if (FD_ISSET(G.netfd, &rfds))
 689 #endif
 690                         {
 691                                 len = read(G.netfd, G.buf, DATABUFSIZE);
 692
 693                                 if (len <= 0) {
 694                                         WriteCS(1, "Connection closed by foreign host.\r\n");
 695                                         doexit(1);
 696                                 }
 697                                 TRACE(0, ("Read netfd (%d): %d\n", G.netfd, len));
 698
 699                                 handlenetinput(len);
 700                         }
 701                 }
 702         }
 703 }